anyname DD Statement

A DD statement must be included for each permanently mounted or mountable volume referred to in the job step. These DD statements are used to allocate devices.

The DD statement should be coded:

  //anyname1 DD UNIT=xxxx,VOL=SER=xxxxxx,
DISP=OLD

The UNIT and VOLUME parameters define the device type and volume serial number. The DISP=OLD specification prevents the inadvertent creation of a data set.

You can also code the DSN parameter to identify a volume, if the data set you name resides on that volume. When unloading a data set from one DASD volume to another, this parameter is required for the data set to be unloaded. An unloaded data set on a DASD volume can only be loaded to the same device type from which it was unloaded.

For mountable volumes, when the number of volumes to be processed is greater than the number of devices defined by DD statements, there must be an indication (in the applicable DD statements) that multiple volumes are to be processed. This indication can be in the form of deferred mounting, as follows:

  //anyname2 DD  UNIT=(xxxx,,DEFER),VOL=(PRIVATE,...),
  //             DISP=(...,KEEP)

Here, the PRIVATE indication in the VOL parameter is optional. Unit affinity cannot be used on DD statements defining mountable devices.